Real Water Saving Using Crop Substitution in Cropping Pattern: A Case Study of Khuzestan Province, Iran

Real water saving is a important concept in water resources management, which can express previous failures in reducing agricultural water consumption, despite increasing irrigation efficiency. In the present research, while calculating the water requirement for the cultivation of the cropping pattern document in Khuzestan province of Iran and harvesting the intended yield, the crop substitution and changing the planting date method (in four scenarios) has been considered as a sustainable solution to reduce the actual agricultural water consumption. Scenarios 1 to 4, respectively, included replacing part of the cultivated area of sugarcane, fodder corn, and rice with sugar beet, fodder sorghum, and sesame, in 3 consecutive years, and changing the planting date of watermelon and tomato from summer to winter in 1 year. For this purpose, the actual evapotranspiration was determined using FAO-56 Penman–Monteith equations and the expected crop yield at the county scale. Then, using the history of cultivation of different crops in each county and the subwatershed map of the Khuzestan province, the actual evapotranspiration, net irrigation requirement, and water withdrawal from rivers in each subwatershed of Khuzestan province were determined. Results showed that implementation of scenarios 1, 2, 3, and 4 can reduce 551, 25, 194, and $79{\mathrm{hm}}^3$ of actual water consumption and decreases 2,160, 104, 775, and $303{\mathrm{hm}}^3$ of water withdrawal, respectively. If all the scenarios are implemented together, it can be expected that the reduction in actual agricultural water consumption and its water withdrawal will be equivalent to 5% and 20% of the rivers discharge in Khuzestan province, with a probability of 80%. By considering the real water saving, economic, and social criteria, it can be concluded that replacing sugarcane with sugar beet is the first priority of implementation, whereas changing rice with sesame is the last priority of implementation.

Water reduction consumption is one the most challenging issues in agricultural water management. We know that agriculture consumes mostly fresh water to produce all kinds of agricultural products. The water is converted from liquid to vapor and removed from the target catchment area by atmospheric currents. Therefore, one of the most useful ways to reduce actual water consumption in agriculture is to improve the cropping pattern. Modifying the cropping pattern can challenge the indigenous knowledge of farmers and affect their habits as well as reduce the income of local communities in some cases. Therefore, it is important to pay attention to the profit of the replaced crop and the level of familiarity of the farmer with how to cultivate it in determining the cropping pattern. This research examines the modification of the cropping pattern in Khuzestan province of Iran, which includes replacement of sugarcane, fodder corn, and rice with sugar beet, sorghum, and sesame, respectively, to reduce agricultural water consumption. For this purpose, the reduction of water consumption, reduction of farmer’s income, and social tendencies have been seen in the defined scenarios.